Stabilized copper bronze powders and method



.bronzes 9f commerce.

United States Patent STABILIZED COPPER BRONZE POWDERS AND METHOD VictorM. Willis, Dolton, Ill., assignor to The Sherwinggiliams Company,Cleveland, Ohio, a corporation of No Drawin Application 18, 156 I 7Serial No. 591,794

17 Claims. (Cl. 106-296) This invention relates to an improvement incopper bronze powders whereby coating compositions containing the samemay be admixed for longer periods prior to use without deterioration ofthe fluidity necessary to application. More particularly, this inventionrelates to a method of treating copper containing bronze powders so asto impart additional stability to said powders when incorporated insolutions of nitrocellulose lacquers for coating purposes.

If copper bronze powders now available as standard articles of commerceare admixed with organic solvent solutions of nitrocellulose lacquers,within a brief time a green coloration develops and shortly thereafterthe liquidity of the system is lost and the product undergoes a sol togel transformation. This phenomena is peculiarly a characteristic ofcopper containing bronze powders, but in the case of other bronzingpowders, such as aluminum bronzes, the difiiculty is not known to exist.

The principal object of this invention is, therefore, to provide acopper containing bronze powder characterized by improved stability whenin contact with nitrocellulose lacquers in solution. The principalobject of this invention can be accomplished at two different timeintervals. It has been found preferable to accomplish the object of thisinvention by a special treatment of the copper containing bronze powderprior to its incorporation in lacquer containing protective anddecorative coatings.

It is also possible, however, to obtain a similar result byincorporating into the nitrocellulose lacquer .solution a quantity ofthe protective additive prior to incorporating therein the copper bronzepowder or within .a very brief but reasonable period subsequent to theincorporation of the copper bronze powder in the bronzing lacquersolution. Time of addition is not particularly critical. However, aspreviously indicated, it is preferred that the treatment take placeprior to the incorporation of the copper bronze powder into liquidbronzing medium. It may be feasible to incorporate the herein describedprotective additive during the copper bronze powder manufacturingprocedure, by addition at one or more stages in comminution of the metalparticles as they are transformed from nodular particles into rela-'tively thin larnellar flakes characteristic of the metal The essentialcomponents of this invention comprises-copper bronze containing powder,an organic compound selected iiGiTr the g p consisting of waterinsoluble long chain aliphatic and.

alicyclic hydrocarbon acids containing from 8 to about 32 carbon atomsas an ancillary agent in conjunction with the metallic copper bronze offrom about one half percent to about five percent by weight of saidbronze powder and at least about five-tenths of a percent but not morethan about ten percent by weight of said metallic powder of a waterinsoluble rosinamine.

Ratio of fatty acid to amine may vary within appreciable limits. Wherethe ratio of acid to amine is within the range of 1:7 to 3:1 the rangehas been found satisfactory for the purposes of the invention.Preferably, the total ce l 2 amount of organic agent in conjunction withthe metallic copper bronze powder has been found to be in excess of onepercent but less than eight percent and the range of acid to aminewithin the ratio of from 1:5 to 2:1. From this range it can be seen thatthe proportions of r'os'inarnine to fatty acid need not be instoichiometric equivalents. It is believed that the optimum range isquite close to stoichiometric equivalents, although this relation hasnot been established by scientific tests.

Copper containing metal, bronze powders for the purposes of thisinvention are generally prepared by subjecting the desired metal to apreliminary comminuting process to reduce the size of the metal toconvenient but relatively large initial particle size. The comminutedmetal particles are then placed in a ball mill, stamping mill, or otherdevice together with fatty acid lubricant containing from eightto thirtycarbon atoms and the metal powders subject ,to the internal forces ofthese mills until reduced to the requisite particle dimension. If it isintended that the final: powders be used as non leafing bronzes, thepercentage of fatty acid may be of the order of one half percentbut'ifffo'r leafing quality the percentage by weight ofthe metal is ofthe order of 2 to 5%. In certaininstances the product is also furnishedas a metal paste. This general practice, in these instances,jto addvolatile thinner to the extent of 20 to 4 0 percent ,to producemetalpowder pastes.

In accomplishing t'heends of thisinvention it is unnecessaryto alter'aippr'eciably the prior art processes for preparation of *therii'etalbronze powder. It is reasonable to assume that little difliculty is tobe encountered in inclusion of the additive of this invention duringbronze powder manufacturing. 'There'is evidence to indicatepreferredresults are obtained if the metal powder, per se, is subject totreatment rather than to cause treatment to occur in the lapquersolutionupongformulation of bronze coatings. v i

In initial stages of development 'of this invention advantages of theadjuvant here disclosed were investigated b'y adding approxiinately 50grams of commercially available copper containing bronze powders(already treated with from one and one half 'to five percent of fattyacid containing atleast 8 carbon atoms) in 150 parts of astandardbroiizingdacquer (lacquer made as set out in Example 1'); Tothe'thus prepared bronzing coating composition was addedexploratorypercentages of various agents which weredeemed to havepotential value in stabilizing the coating composition against changesin its viscosity and to prevent attendant gelation occurring shortly(1-4days) after mixing of the bronze powder with nitrocellulose lacquersolutions.

Through this series of tests it was found that a generic class ofmaterials 'comrnonly described as rosinamines were usefulin's'tabilizing the bronze containing lacquer coating. By the termrosinamine as used herein, it is intended to refer tocommercially'available products in which the parent compound containsfrom about percent to 97 percent of the primary amino compound derivedfrom rosin. 'The parent group of compounds includes rosinamine,dehydr'orosinamine, dihydrorosinamine, and v te rahysiroresinamine. Aseries f ag g tests has established the parent primary aniind compohhdto be preferred for the purposes of this invention. However, a morecomprehensive testing of it and related compounds has also shown it tobe within the scope of the invention to use secondary rosinamines whichare alkylene oxide condensations of the parent primary rosinaminecompound. is possible when the quantity of the alkylene oxide condensedwith the parent primary rosinamine is small. In no case should enoughalkylene 'oxide (ethylene oxide) be condensed with the rosinarnine torender the so diarived secondary rosinamine water soluble, or tointerfere with the basic character of rosinamines. Thus, both primaryand secondary rosinamines are useful for the purposes of this invention,although as stated previously, primary rosinamines appear to be moreefiective. The non-substituted primary. and secondary rosinamines usefulfor the purposes of this invention are characterized by an organicresidue of a structure similar to the structure of abietic acid, whereinvthe carboxyl group of the abietic acid issubstituted for with an aminogroup. While primary amines are preferred, the secondary rosinamines(whereinone of the active hydrogens of the parent amine is replaced by'alkylene oxide condensation) are usef u1 to accomplish a similarresult. The amount of ethylene oxide, which can be tolerated incondensation with the primary rosinamine, is insufiicient to render theso-formed secondary rosinamines water soluble. To illustrate, thelimitation of the term water soluble" as it appliesto these compounds isas follows:

when 11 molesormore of ethylene oxide are condensed with one mole of rosinamine sufficient instability is observable in the resultantbronzinglacquer coatings to remove this agent from practi cal value andto eliminate it from consideration. for the purposes of this invention.

If seven moles of ethylene oxidearecondensed per mole of primaryrosinamine, there isstill some water solubility and the usefulnessjsappreciably lostfor my purpose. However, if the arnount of ethyleneoxide is reduced to five moles per molepf rosinamine, the secondaryamines resulting are useful and the solubility iniwaterat this range isnegligible. The expression ff'water insoluble rosinamine" has thereforebeenjarbitiarfly'limited and does not embrace secondary rosinaniin escontaining more than eleven moles of alkylene, oxide per mole ofrosinamine. While experience hasgbe en primarily with ethylene oxideadducts-of rosinamine it is obvious that propylene oXideaddu tsarealspotentially available. It should be pointed out ,that water solubilityper se, is not known to be a detrimental quality in the; presentapplication. Water solubility does provide, however, a convenient meansof lirnitingand defining,the scope of rosinamines of secondary natureuseful iforpurposes of the invention with practical accuracy in thehereinafter appended claims. a In A'review of the prior artwhigh relates'to the production of metal pastes, pigments, aluminum; bronzcs, andcopper containing bronze, powdersestabli shes that it is customary inthe art of manufajcture'ofimetal powders for pigment use to employ longchain fatty acids to promote the leafing quality of the" metali powdersand to lubricate the metal as it is transformed from the larger particleshrode state to.a fine particle lamellar powder state and to assist inpolishing the surface of the finc metal powder particles to obtainoptimum brilliance. The prior art discloses a numberof fatty acidsuseful during attenuation of metal toa finely powdered lamellar state.Among the organic compounds selected from the group consisting of waterinsoluble long chain aliphatic and alicyclic hydrocarbon acidscontaining from 8 to about 32 carbon atoms reportedly usedare sunfloweroil acids, ricinoleic acids (castor oil a ids), Qleic acids, myristicacid, palmitic acidQnaphthenic acids, etc., which are characterized bytheir lubricity, water insolubility. and soap forming qualities. In thearts which relate to surface activity, it is generally recognized thatsurface active qualities of long chain aliphatic acids are of littlemoment until the fat-l1 acid contains. at -least 8'carbon atoms in itshydrocarbon chain. "Most surfacefactive agents contain from eight toabout 32' carbon atoms in their longest hydrocarbon chain. For thepurposes of this invention, long chain aliphatic and alicyclichydrocarbon acids within this range are useful and essential inconjunction with the described rosinamines to accomplish'thecnds of theinvention. 1

As will be shown in the examples, presence of rosinamine alone, inconjunction with the metallic copper bronze powder appears to hastengelation when in conjunction with a dispersion of the metal powder in asolution of a nitrocellulose lacquer. It has been observed the presenceof water in macroscopic quantity also hastens gelation ofbronze-containing lacquers, independent of the treatment or method oftreatment as described herein. However, it is known that quite smallamounts of water are present in nitrocellulose as shipped commerciallyfor it is wetted down with about 30 percent of ethyl alcohol. The ethylalcohol in turn contains water. This water is carried into bronzinglacquer formulations. The amount so carried in appears not to interferewith the effectiveness of the treatment herein described.

A host of related amines have been used in comparative manner to therosinamines herein described. These amines include alpha naphthol amine,paraphenylenediamine, and diphenylguanadine. In each test case theuseful life of the completed bronzinglacquencontaining the recitedamines was seriously diminished.

The following examples, while numerous, are by no means to be construedas exhaustive. They are included to illustrate the best methods ofpractice of the invention and to make clear, by comparison, limitationsupon the invention and to illustrate the difference between what is hereaccomplished and what has been illustrated in the prior art. It is to benoted in passing that attempts to artificially accelerate the age rateof test samples by exposing them to elevatedtemperatures were in allcases unsatisfactory. This for the reason that-developed fluidity of thenitrocellulose suspending medium allowed rapid settling of the heaviermetallic bronze powder into closer proximity of the individual metallicflakes and entrapment of thin films of nitrocellulose lacquer betweenrelatively large active metallic surfaces of the copper bronze powder.These conditions appeared to cause very rapid reaction to take place.Increasereactionrates were observed at temperatures of the order of l25F. Test results recorded herein were at room temperature and with in therange of 65 to 90 F. Partsare by weight unless otherwise identified.

EXAMPLE I EXAMPLE H (Control) Parts Cordova rich gold 49 Copper bronzepowder Stearic acid L25 Lacquer of Exam le I 150 were aged together atroom temperature.v At thecnd of 4 days, the previously liquid sample hadundergone a sol to gel transformation and discolored to a characteristiccopper-green color.

EXAMPLE III Parts Cordova rich gold 49 Copper bronze powder Stearicaoirl 1.25 Rosinamine 2.50

Lacquer of Example I 1S0 Acetone asserts were mixed together and aged atroom temperature. At the end of 30 days the sample was still usefulfor'paint purposes.

EXAMPLE IV Part A 200 parts copper bronze were exhaustively extracted ina soxhlet apparatus for 2 hours with chloroform to PartB Parts Treatedbronze from above 50 Std. lacquer solution 150 were mixed together. Uponovernight age, a solid gel formed. Control: gelled in 4 days. Theexample illustrates ineffectiveness of rosinamines alone.

EXAMPLE V Parts Copper bronze powder (2 /2% stearic acid) 5O were mixedtogether and after several hours the paste was heated and the acetonedriven off by evaporation. The product remaining still containing someacetone was mixed with 150 parts lacquer of Example I. Thelacquer-bronze mixture had not changed appreciably in viscosity at theend of days at room temperature and behaved normally upon application asa coating.

EXAMPLE v1v The following materials were tested, using 50 parts copperbronze powder, 2.5 parts'test material and 150 parts lacquer of ExampleI. The length of time of stability in each case was recorded as follows:

Rosinamine Identification Material a B-napt Control (No addition) 96 24Carbon atom primary amine 60 EXAMPLE VIII Parts Metal powder (copperbronze) 50 Rosinamine 2 Water 2 Lacquer 150 Test was made to determinetreatment effectiveness if water was present in substantial amount.terial gelled overnight. The test established that water in more thantrace amounts cannot be tolerated in the system and precautions shouldbe taken to maintain the bronzing lacquer system as dry as possible.That trace amounts of water can be tolerated apepars from the fact Testma- 5 6 'that trace amounts of water are present in Bronzing lacquetsolutions prepared as in Example 1.

EXAMPLE IX In a test series, 50 parts of copper bronze powder weretreated with 2.5 parts, (a) rosinamine naphthenate, (b) rosinaminelaurate, (c) rosinamine oc toate, (d) rosinamine oleate. The test runswere found to be in good condition after the control sample containingno rosinamine salt had gelled.

EXAMPLE X the metal containing nitrocellulose solution against gelation.With a molar ratio of 1:1 rosinamine-ethylene oxide adduct added thetreated bronze gelled in 28 days, whereas the adduct containing 1 molrosinamine to 11 mols ethylene oxide gelled in 14 days.

From the behavior of this series, as well as in a comparable serieswhere the rosinamine-fatty acid condensa-- tions were of fatty acidscontaining from 2 to 5 carbon atoms, it was determined that rosinamineadducts useful for the purposes of the invention, again, were preferablylimited to those of water-insoluble nature.

The percentage of rosinamine useful for the purposes of the inventionwas found to be within the range of about 0.5% to not more than about10% by weight of the copper containing metal powder. While effective athigher percentages, the total length of time before gelation fell offrapidly as the amount of rosinamine present was increased above 10%. canuse too great an amount of amine in relation to fatty acid lubricantinherently present in bronzes of commerce for test purposes.

In all theexamples, unless otherwise noted, it is to be observed thatthe copper bronze powders .used as illus trative contained from 2 to 3%of stearic acid.

While it is possible and satisfactory for the purposes of the inventionto add the rosinamine solution to the lacquer solutions and to formrosinamine-fatty acid salts in situ in the bronzing liquid upon'additionof the bronze, it is preferred to form the fatty acid salt of rosinaminedi rectly upon the copper bronze powder, and following this step to makethe bronzing liquid by admixture of the treated bronze powder andlacquer solution.

Having described my invention, what I claim is:

1. A copper-containing bronze powder of improved stabilitycharacteristics which comprises a major quantity of a copper containingbronze powder and in intimate contact therewith at least 0.5% but notmore than about 5% by weight of said metal powder of an organic compoundselected from the group consisting of water insoluble long chainaliphatic and alicyclic hydrocarbon acids containing from 8 to about 32carbon atoms and a waterinsoluble rosinamine.

2. A copper-containing bronze powder characterized by improved stabilitywhen in contact with nitrocellulose lacquers in solution in volatileorganic solvents which comprises a copper containing bronze powder inintimate contact with a mixture containing at least 0.5% but not morethan about 5% by weight of said powder of an organic compound selectedfrom the group consisting of by improved stability when in contact wtihnitrocellulose In this series, it was determined that the This evidencesuggests one Iacquers in solution in volatilqorganic solvents whichcomprises a copper containing bronze powder inintimate contact with atleast five tenths of a percentbut 'not more than about five percentbyweight of said powder of an organic compound selected from the groupconsisting of water; insolubledong chain aliphatic .and lalicyclichydrocarbon acids containing from" 3 to aboutBZ-carbon atoms and a waterinsoluble rosinamine wherethe weight ratio of acid to amine is. withintherange'offrom 1:5 to2:1."

4. As in claim 3, where the alicyclic hydrocarbon acid is napthenicacid.

5. As in claim}, where the long chair aliphatic acid is stearic acid. I

6. As in claim 3, Wherethe long chain aliphatic acid is myristic acid. r

7. As in claim 3, where thelong chain aliphatic acid is palmitic acid.

8. As in claim 3, where the long cbain aliphatic acid is lauric acid.

9. As in claim 3,

rosinamine.

10. A copper containing bronze powdercharacterized by improved stabilitywhenin contact with nitrocellulose lacquers in solution which comprisesa copper bronze containing powder, from one half a percent to notappreciably more than live percent of an organic compound selected fromthe group consisting of. water insoluble long chain aliphatic andalicyclic hydrocarbon acids containwhere the rosinamine is a primary ingfrom 8 to about 32 carbon atoms and from 0.5% to not morethan about. 10%by weight ofsaidpowder of a primary rosinamine.

11. As in claim 10,. .where the alicyclic hydrocarbon 15. Innitrocellulose lacquer solutions in organic solvents containing copperbronze metallic pigments coated with a lubricating organic acid selectedfrom the group consisting of water insoluble long-chain aliphatic andalicyclic hydrocarbon acids containing from 8 to about 32 carbon atomsin association with said copper bronze powders, the method of increasingthe useful life of the above described liquidcoating compositions whichcomprises including. therein during manufacture and prior to storage,from 0.5% to not more than about 8% by weight of the copper bronzepowder in said coating composition of a water insoluble rosinamine.

16. A method of increasing the useful life of copper bronzepowder-containing nitrocellulose lacquers in solution in organicsolvents which comprises including with the copper bronze,nitrocellulose lacquer solution and the 0.5% to 5% by weight of saidbronze of lubricating fatty acids associated with said copper bronzesfrom five tenths of a percent to not more than about 10 percent byweight of the copperbronze powder of a primary rosinamine.

17. A method of increasing the useful life of copper bronze powdercontaining nitrocellulose lacquers in solution in organic solvents whichcomprises including with the copper bronze, nitrocellulose lacquersolution and the 0.5% to 5% by weight of said bronze of stearic acidassociated with said bronze from five tenths of apercent to not morethan about eight percent by weight of said bronze .of a primaryrosinarnine.

References Cited in the file of this patent UNITED STATES PATENTS2,178,181 McMahan Oct. 31, 1939 2,445,374 Van Wyck July 20, 19482,525,280 Allen Oct. 10, 1950 2,561,892 Van Wyck July 24, 1951 2,709,160Korejwa May 24, 1955 FOREIGN PATENTS 180,062 Switzerland Dec. 16, 1935

1. A COPPER-CONTAINING BRONZE POWDER OF IMPROVED STABILITYCHARACTERISTICS WHICH COMPRISES A MAJOR QUANTITY OF A COPPER CONTAININGBRONZE POWDER AND IN INTIMATE CONTACT THEREWITH AT LEAST 0.5% BUT NOTMORE THAN ABOUT 5% BY WEIGHT OF SAID METAL POWDER OF AN ORGANIC COMPOUNDSELECTED FROM THE GROUP CONSISTING OF WATER INSOLUBLE LONG CHAINALIPHATIC AND ALICYCLIC HYDROCARBON ACIDS CONTAINING FROM 8 TO ABOUT 32CARBON ATOMS AND A WATERINSOLUBLE ROSINAMINE.